1. Field of the Invention
This invention in general relates to photography but in particular to photographic camera apparatus by which a camera user is given a visual indication in a camera's viewfinder of the status of a manually operable exposure trim mechanism which is used to vary the control of the camera's automatic exposure system.
2. Description of the Prior Art
Photographic cameras of the type which include systems by which the exposure of a film is automatically controlled in a predetermined manner are well-known in the prior art. In general, such exposure control systems usually consist of an electro-mechanical shutter arrangement which is controlled by the output of a light sensing element in such a way that aperture and/or shutter speed are set in accordance with the film's given ASA speed rating and what the light sensing element judges the "average" scene brightness to be. As examples of such automatic exposure control systems, reference may be had to U.S. Pat. No. 3,975,744 issued to Bruce K. Johnson et. al. on Aug. 17, 1976 and entitled "Automatic Exposure Control System"; U.S. Pat. No. 3,896,458 issued to Bruce K. Johnson et. al. on July 22, 1975 and entitled "Automatic Exposure Control System"; and U.S. Pat. No. 4,035,813 issued to George D. Whiteside on July 12, 1977 and entitled "Exposure Control System For Selectively Determining Exposure Interval".
Although these automatic systems have remarkably good exposure performance for the majority of scene lighting conditions normally encountered in photographic work, certain types of scene lighting situations--particularly those known as "high-contrast"--do exist which require an exposure which is different from the "average" which would normally be predicted by the automatic exposure control system's light sensing element. Therefore, when an anomalous scene lighting situation like a strongly back-lit scene is encountered, the light sensing element will predict an "average" exposure which for back-lit conditions will be less than that necessary to capture the more important details of the scene. The effect of such underexposure, of course, will be that the picture's primary subject will be darker than desired.
Those skilled in the photographic arts have recognized that the automatic type exposure control system has this peculiar exposure control problem in dealing with "high contrast" lighting situations and have solved the problem by providing exposure "trim" arrangements by which a photographer can manually change the response of the light sensing element of the exposure control system and thus its output which in turn causes the film to be exposed either more or less than it would otherwise be if the system were allowed to operate at its "average" or nominal setting. Thus, with these "trim" arrangements the photographer has a degree of discretionary control over what the exposure will be and can exercise it according to his personal preference and judgment regarding how much departure from the "average" setting is required for the particular scene being photographed. For such trim arrangements reference may be had to, for example, U.S. Pat. No. 3,832,721 issued to Irving Erlichman on Aug. 27, 1974 and entitled "Lockout Mechanism For Automatic Trim Assembly Return Mechanism" and U.S. Pat. No. 4,007,468 issued to Igor Blinow et. al. on Feb. 8, 1977 and entitled "Trim Control Apparatus For Photographic Exposure Control System".
While the aforementioned manual exposure "trim" arrangements and others which are functionally similar allow for the exercise of a degree of personal control over exposure to accommodate the anomalous scene lighting condition, a photographer must generally remember to reset them to their nominal position after having made a change for the anomalous scene. Otherwise the "average" scene which accounts for the majority of pictures taken will be misexposed. Therefore, it is the primary object of the present invention to provide photographic camera apparatus for use with cameras having automatic exposure control systems with a means by which a camera user is provided with a visual indication, preferably in the camera's viewfinder, that an exposure trim mechanism is set in one of its positions other than its "average" or nominal one so that the user can adjust the trim mechanism to a position which he prefers.
Other objects of the invention will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, the combination of elements, and arrangement of parts which are exemplified in the following detailed disclosure.